A one-to-one conversation lasts 15 minutes because it is comparable with the economic value used for your booking, that is, the value of a single talk. If you think you want to spend more time with the tutor there are two possibilities.

1. Reserve 2 or more one-to-one conversation slots
2. Ask the tutor that you want to use the conversation extension option. That is, at the end of the 15 minutes it is possible to use an additional talk (token) to continue for another 15 minutes.